First, get an ODBII gauge (scangauge2, or a bluetooth adaptor with an APP for your phone or spare tablet)..

It's VERY common for the thermostat to keep your engine "cold" which will cause your engine to burn more fuel. 190* and above is where you want your coolant temp, typically a 2 year old stock t-stat likes 179* which kills your MPG.
Now that it's in the 70s/80s here in FL, my OEM t-stat is once again screaming for a replacement...

MONITORING your 6L is the FIRST step, you might find (as has been stated above) alternator, FICM, or other lingering issues which once fixed will improve your MPG - AND make your truck run better and LAST longer.

The 4WD (and tow mirrors) impact MPG, so you have to live with those factors.
Keep your highway RPMs close to 2k and just enjoy..

 

The Edge CS and CTS can be set to alarm at a given parameter along with recording max temps. Check them once a week and not worry about your wife watching gauges instead of the road.

 

over here you get run over too - need to keep over 60mph to be quicker than the trucks as they are limited to around 55 in Europe, and hate going slower.

wife was actually getting around 14mpg cruising empty at 85-90 which I thought was OK - not the speed, the mileage

 

When it comes for fuel economy on a 6.0 there are MANY factors to take into consideration.....

A few things to consider based on your 2004 truck....

-Is your EGR valve clean? Whether or not you have an "inferred" or are fortunate enough to have a "non-inferred" PCM stategy, the EGR valve plays an important role. If the EGR valve has never been cleaned, pull it, clean with carb cleaner, and reseal with new O-rings.

-Your EBPS or Exhaust Back Pressure Sensor plays a role in the fueling of the truck if you have a "non-inferred" PCM calibration. The truck fuels and spools the turbo based on EBP in non-inferred calibrations. In inferred calibrations, it's still used as a Vref and still needs to be in working order. Furthermore, either the tube, sensor, or fitting at the exhaust manifold may be plugged with soot. On a 2004 truck, this sensor is located on the thermostat housing. Follow the tube down to the driver side exhaust manifold and remove. You'll need to use a wire brush and gasoline or carb cleaner to clean and clear the tube. Once it's cleared, use the same (now bristleless brush) to clear the fitting at the exhaust manifold, this is almost always what the problem is with the EBP.

-The MAP nipple on the intake manifold is also something that limits these trucks due to the EGR. Soot from the EGR, circulates and clogs the nipple. With the MAP nipple clogged with soot, the PCM can no longer accurately tell how much boost is coming into the intake manifold, which in turn limits the fuel the PCM feeds the engine, which leads to poor fuel economy and power. You can clear the MAP nipple with a wire hanger, DO NOT spray anything into the intake manifold.

-As Steve and others have mentioned, the health of your FICM also plays a role in fuel economy, power, and the overall performance of your engine. Make sure it, along with your batteries, and alternator are in good shape. If you still have the dinky, small case, 110 amp alternator, consider upgrading to the 140 amp large case alternator, it does a much better job of charging and supporting the truck. It's not the end all solution, but is better than something that if you ask me is barely adequate to keep up with the electrical demands of the truck.

-Fuel pressure is critical, it should never drop below 40 under any circumstances and if it does, replace the FPR with the new blue fuel spring, and if the pressure is still low, perform a static test on the pump itself as it may be on it's last leg. Keep in mind, when a 6.0 pump is dying, it gives absolutely no warning. A 7.3 pump will sound like angry bees, but a 6.0 pump sounds normal and will fool the most skilled mechanic unless the know what they're looking for. Ask me how I know....

-The correct motorcraft filters are another question to ask. When was the last time the air, fuel, or oil filter were changed? Were they motorcraft filters? If you don't know, replace them and go from there.

-Seeing as this truck is a 4wd truck, are the hubs disengaged? If both or even one side is locked, it can shave a few mpg off. Again, ask me how I know...clockwise to lock, counter clockwise to unlock. With the hub unlocked, back up 20-30 feet and they should unlock, if not, you have issues.

-PCM, TCM, and FICM calibrations. These are actually more important that you think and will lead to the next thing to look at. You'll need someone with an SCT programmer to pull your stategy. If your strategy starts with VXCB1, VXBC3, or VXBC6, these are non-inferred PCM calibrations that should yield good fuel economy and power. If your strategy starts with VXBC7 or VXBC9, these usually aren't good calibrations. VXBC9 is inferred and does not use the EBPS between it and the FICM calibration matched to most of the VXBC9 calibrations, it causes trucks to drink down fuel while severely limiting performance.

-How healthy are your injectors? This is another question to ask especially with the PCM and FICM calibrations in mind. The later FICM calibrations are specifically designed to help make cold start issues a thing of the past and save Ford warranty dollars while these trucks were covered. ARZ2AH10 for 2003 trucks, ARZ2AL10 for 2004 trucks, and ARZ2AL11 for 2005-2007 trucks. These FICM calibrations saved Ford warranty dollars two ways: they are severely detuned to limit fueling from strong PCM calibrations and tunes. These specific calibrations also compensate and effectively cover up weak injectors. For example, if an injector can only produce 80% of what it commanded, the FICM brings the other injectors down 20% to compensate effectively reducing fuel economy and power.

-The above being said, if you live in a colder climate, consider running B20 along with Ford's PM23 fuel additive/antigel. Over time, this will work injectors with a sticky fuel side free. On the oil side of the injector, consider Archoil 9100 with 5w40 oil. It will take up to three oil changes depending on how bad potential stiction is, but this is a very effective stiction eliminator.

This should leave you with a very healthy truck and/or at the very least help you work through any issues that may be present limiting your truck's performance.

 

Nice post Razzi

 

Man TD, It'd take me a 1/2 day to type all of that. I'm jealous.

 

Heard he has 20 fingers

 

What was the benefit of this change? Ford obviously did it for a reason. Perhaps to keep warranty trucks out of the shop?

Do most of the good 6.0 tuners go back to a non-inferred strategy to improve MPG or are you stuck with it on the VXBC9?


Babying my 2005 at 65mph on a long high way trip, unloaded, with stock VXBC9 programming I was able to net a little over 19mpg (hand calculated). 4x4, stock height, 275/65/18 highway tires at 50psi for comfort, Rotella 5W40 synthetic motor oil, synthetic oil in diffs and Xfer case. Not bad I think?

Cold starts and short trips kill mpg. 7-mile commute to work with about 12 stop lights, truck doesn't reach 190 until mile 6 on a cold morning. Average 13mpg for the trip according to the "calibrated" mpg meter on the scan guage! Still better than a V10 on the highway though!

 

Thank y'all very much, just paying forward what I've learned.

Correct, It was really for several reasons, but mainly:

To add to that, the fuel limitations were imposed on the FICM and PCM calibrations. This was to prevent head gasket failures due to customers still under warranty running programmers.


Depends on who you talk to...

PHP pioneered and proved that earlier PCM and FICM calibrations yielded better power and fuel economy than later strategies. If you get tunes from them and have a later flash, they'll more than likely write you back to an earlier strategy and suggest one of their FICM flashes (Econo, Atlas 40, 80)

Gearhead- Ask and you shall receive

Quick Tricks Auto- Prefers the later strategies, but with some convincing can write you back.Tony Wildman- Not sure, haven't been able to catch this guy

Eric at Innovative- Ask and you shall receive




Not bad at all really, but there are two things wrong: VXBC9 is for a 2004 truck and given that yours is a 2005, you should have VXCF9. You're also missing the two most important parts of the strategy: the last two letters. The last two letters are basically a revision of the base strategy and the difference between the following vehicles:

-Excursion
-F250/350/450/550, manual or auto, California emissions, Federal Emissions, etc

What are the last two letters?

There are some good versions of VXBC9 and VXCF9 that actually work quite well, they're few and far in between, but they do exist.


Back on topic for the OP....

 

My bad, I thought just the "9" part mattered and I just copied what was posted earlier. Checked it, and it's a VXCF9DB flash.

 

I will second what TD says about the health of your FICM. See my post on the Atlas 40 and FICM rebuild I just R and R'd........made a world of difference, and got rid of the bad Ford reflash.

 

When I have had drops in fuel economy, I have found issues with the following (as others have previously posted):
tire pressure
brakes dragging
hubs locked
weak FICM and/or injector issue

What others have said above (good posts above folks and apologies if I am regurgitating some things posted earlier) plus a few other things:
Make sure all your sensors are accurate (EOT, ECT, EBP, MAP, MAF, IAT's, etc)
Check for boost or charge air leaks
Minimize idling and A/C usage
lifts and larger tires (as well as the type of tire)
aftermarket mods that increase wind drag
Use of the air conditioner drops fuel economy (I see about a 0.5 mpg drop with mine)
Some trucks are inherently going to get slightly lower fuel economy than others based on their "options" (ie dually's, 4WD, crew cabs, differential ratios, PCM strategy, etc.)
proper maintenance helps (filters, fluids, etc)
dragging accessory - say like an A/C compressor

In the winter, my fuel economy drops. Some say it is winter fuel, but here in Texas, I don't really think that is so much the case. I believe that it is built into the engine strategies. I also believe that using your block heater will help some with the fuel economy. A cold engine uses more fuel and electrical heat is more efficient than burning diesel by idling!

But by far the biggest impactors that I have seen are speed, driving style, and driving into a stiff head-wind!

FYI - from Ford:
6.0/6.4 Fuel Economy:
Ford vehicles equipped with the 6.0 PowerStroke diesel are not rated for fuel economy by the EPA. If economy is in question, a boost test should be performed. If boost reaches 22-25 PSI in third gear, wide open throttle under load, then the engine is operating normally and no economy related repairs need to be performed. If not in specs, then the engine will need to be diagnosed--check sensor reading, VGT and EGR operation, fuel pressure and quality, crankcase pressure, intake or exhaust restriction, exhaust or CAC leaks.
Fuel economy will be affected by many factors, including: excessive idle time (one hour equals approximately 33 miles of driving), fuel quality and blend, ambient temperature, driving habits, vehicle use, towing, loads, add-on accessories. Broadcast Message 1271, 4450, 6989

 

I did a lot of fuel tracking years ago, and playing around with fuel mileage. Hand calculated I've gotten close to 22mpg at times but you have to really work at getting that. It is also for my mostly flat coastal NJ region and light traffic highways with minimal local traffic. Some od this others have stated and my programming is the original pilot injection that came with the truck.

Tires need to be stock, no increase in size with pressures at 75 in the front and rears at 65 with no weight being carried. Bed cover, synthetic lubricants, no A/C, speed 55-60 max, in neutral downhill and approaching off ramps, stop signs, stop lights, etc. Idle in neutral anytime stopped (it's amazing how much this truck pushes at idle). Draft behind trucks and busses at a safe distance (NJ is usually close), but tractor trailers provide the most "pull".

I find that winter air temps, no so much winter fuel gives lower mpg, but I've improved that by blocking some air flow through the radiator. Jersey also usually has a warm spell the second or third week in January and my mpg always kicks up then. I've also run my farm (but taxed) fuel well into cold weather and not seeing any difference between the fuels at changeover.

And as Mark said above I've seen improvement in cold weather by using the block heater to prewarm, not so much as a starting aid.